1. Field of the Invention
The disclosed technology relates to a stretchable electronic device comprising a stretchable interconnection electrically connecting two electronic components of the device, and further relates to a method of making such stretchable electronic device.
2. Description of the Related Technology
It is known to build electronic circuits on flexible substrates such as plastic substrates. Flexible circuits are often used in applications where flexibility, space savings, or production constraints limit the use of rigid circuit boards.
It is further known to connect electronic devices with the aid of stretchable interconnections. Such stretchable interconnections allow for relative movement of the electronic devices with respect to each other.
Maghribi et al (US2004/0243204, US2008/0026138, U.S. Pat. No. 7,265,298) describe a stretchable electronic apparatus and a method of producing the apparatus. The apparatus comprises a stretchable polymer body, and at least one circuit line extending in the longitudinal direction and having a longitudinal component that extends in the longitudinal direction, and at the same time an offset component that is at an angle to the longitudinal direction. The metal features are patterned (deposited) on the stretchable polymer body. Serpentine circuits are used in the electronic circuit.
Franz et al (US2004/0129077) describe a system comprising an overload protection to limit the deflection of a spring system. The sensor is implemented in a micromechanical structural component and has parts which are movable in relation to the stationary substrate of the structural component. It includes an unsupported seismic mass, a spring system having at least one spring, the seismic mass being connected to the substrate through the spring system, an overload protection to limit the deflection of the spring system and the seismic mass in at least one direction, and means for detecting the deflections of the spring system and the seismic mass. Design measures are proposed whereby the impact forces may be reduced to prevent conchoidal breaks and resulting incipient damage to the sensor structure as well as formation of particles. To that end, at least one two-dimensional stop for at least one moving part of the sensor structure is provided as overload protection. Alternatively or in addition thereto, at least one spring stop for at least one moving part of the sensor structure is provided as overload protection.
In “Design and fabrication of stretchable multilayer self-aligned interconnects for flexible electronics and large-area sensor arrays using excimer laser photoablation”, IEEE Electron Device Letters, Vol 30, No. 1, 2009, K. L. Lin et al describe a fabrication process for stretchable multilayer interconnects on polymer substrates wherein metal patterns are used both as functional interconnect layers and as in situ masks for polymer excimer laser photoablation. This fabrication process is based on a sequential build-up approach. The process starts from a polyimide sheet onto which a metal is deposited. The metal is patterned and another layer of polyimide is applied by spincoating. A second metal layer can then be applied and patterned. The metal is used as a mask during the laser ablation of the underlying polyimide layer. In this way, free standing stretchable interconnections are created. This approach, that is based on removing excess material (by laser ablation) to obtain a stretchable structure, may lead to a time consuming, material consuming and non cost-effective fabrication process. Integration of electrical components with the free standing stretchable interconnections is not discussed.
In U.S. Pat. No. 7,487,587 a method for the fabrication of stretchable electronic circuits is described, using an alternative approach. In a first process patterned metal features are formed on a sacrificial (temporary) substrate. Next components are mounted and then a stretchable and/or flexible material is provided for embedding the patterned metal features and the components. After that the sacrificial substrate is removed. Optionally a second set of components can be mounted at the side where the sacrificial substrate is removed and this second set of components can be covered with a stretchable and/or flexible material. It is an advantage of this approach that the components are provided in an early stage of the process, such that they can be soldered. However, this approach only allows single level metallization. For conductor crossovers one needs to provide zero Ohm cross-over resistors in the stretchable circuit part.